Inland Sea Of Japan Research Articles

Elucidation of the history of coastal utilization of the Setouchi islands, Japan by multifaceted analysis and three-dimensional geological modelling

Three of the four main islands in Japan are separated by the Seto Inland Sea in the country's Setouchi region. This area is an important inland sea of Japan and is interesting for researchers in various fields because of its historically active exchange and trade. Associate Professor Keisuke Makibayashi, Research Center for Asian Archaeology of Industry and Culture, Ehime University, Japan, is involved in a project focused on the Miyan'na site, which is a salt-making site from the Kofun period and the Kamakura period on a small island in the Seto Inland Sea in Ehime Prefecture that is seeking to restore the lost landscape. This work involves the use of different research methods such as particle size analysis, soil physics and chemistry analysis, as well as organising a cross-sectional view of the Miyan'na site, performing 3D geological modelling, using scientific data to explain beach ridges and understand historical human activities, and performing excavations. Ultimately, the researchers want to return the landscape to the local community, thereby contributing to the people in the area. The research is also expected to make important contributions to archaeology, history and environmental science.

Importance of light status on phytoplankton biomass in the turbid Bisan Strait, Japan: results from a high-frequency sampling study

AbstractThe dynamics of phytoplankton biomass in the vertically mixed south-eastern part of the Bisan Strait, in the Seto Inland Sea of Japan, may be considered to be strongly dependent not only on nutrients but also on light status. This was investigated by examining variations in chlorophyll-a (Chl-a), nutrients, and Secchi-disc depth through high-frequency sampling (a mean of once every 1.7 days) at the same station from April to October 2019. Precipitation during the Japanese rainy season (East Asian monsoon rains) was associated with a decrease in salinity from 32 to 31 in late July. The highest concentration of dissolved inorganic nitrogen (DIN), the most deficient nutrient, also was recorded in late July in association with seasonal precipitation. However, the measured Chl-a peak (max. 4 μg l−1) in early August was not as high as expected, possibly due to low water clarity. A relatively small but substantial peak of DIN (max. 4 μM) was recorded in mid-August, which coincided with the passing of a typhoon. The small peak of DIN coupled with higher water clarity thereafter was followed by a phytoplankton bloom from mid-August to early September, at which the highest Chl-a (7 μg l−1) occurred. It is suggested that increased light penetration enhanced the efficiency of nutrient assimilation and thereby triggered the late-summer phytoplankton bloom. In contrast to the adjacent stratified areas, light rather than nutrient status appears to be the key determinant for the onset of phytoplankton blooms in the Bisan Strait.

Comparative analysis of the ecosystems in the northern Adriatic Sea and the Inland Sea of Japan: Can anthropogenic pressures disclose jellyfish outbreaks?

A prominent increase in the moon jellyfish (genus Aurelia) populations has been observed since 1980 in two semi-enclosed temperate seas: the northern Adriatic Sea and the Inland Sea of Japan. Therefore, we reviewed long-term environmental and biotic data from the two Long-Term Ecological Research (LTER) sites, along with the increase in the moon jellyfish occurrence to elucidate how these coastal seas shifted to the jellyfish-dominated ecosystems. The principal component analysis of atmospheric data revealed a simultaneous occurrence of similar climatic changes in the early 1980s; thereafter, air temperature increased steadily and precipitation decreased but became more extreme. Accordingly, the average seawater temperature from March to October, a period of polyps' asexual reproduction i.e. budding, increased, potentially leading to an increase in the reproductive rates of local polyp populations. Conspicuous eutrophication occurred due to the rise of anthropogenic activities in both areas from the 1960s onwards. This coincided with an increase of the stock size of forage fishes, such as anchovy and sardine, but not the population size of the jellyfish. However, by the end of the 1980s, when the eutrophication lessened due to the regulations of nutrients loads from the land, the productive fishing grounds of both systems turned into a state that may be described as ‘jellyfish-permeated,’ as manifested by a drastic decrease in fish landings and a prominent increase in the intensity and frequency of medusa blooms. A steady increase in artificial marine structures that provide substrate for newly settled polyps might further contribute to the enhancement of jellyfish population size. Elevated fishing pressure and/or predation by jellyfish on ichthyoplankton and zooplankton might jeopardize the recruitment of anchovy, so that the anchovy catch has never recovered fully. These semi-enclosed seas may represent many temperate coastal waters with increased anthropogenic stressors, which have degraded the ecosystem from fish-dominated to jellyfish-dominated.

Marine sedentary communities with special reference to the succession in the Inland Sea of Japan.

Marine sedentary communities with special reference to the succession in the Inland Sea of Japan.

Transit vessel scheduling

A transit vessel traffic scheduling algorithm has been developed to limit the negative effects on cargo volume throughput in two-way waterways where separation distances between transiting vessels must be maintained and passage restrictions may hold. It runs in time that is polynomial in the number of ships involved in the computation and finds schedules which increase the utilization of waterways. Three examples illustrate its use. The first example is situated in the Sunda Strait where the algorithm is used to enhance the safety of merchant shipping against a terrorist threat. It illustrates important features of the algorithm and demonstrates how it can be used with cross traffic. The second example is situated in the Strait of Istanbul and offers a comparison between the developed algorithm and the transit vessel scheduling algorithm of Uluscu et al., J Navig 62 (2009), 59–77. This was done using a plausible model of the Strait of Istanbul. The third and last example shows how the algorithm can be used to schedule transit vessel traffic in two-way waterways with junctions. This feature is especially useful in congested waters with a high risk of collisions like the Inland Sea of Japan. An extreme test case proves that the developed algorithm is a practical algorithm ready for such use. © 2017 Wiley Periodicals, Inc. Naval Research Logistics 64: 225–248, 2017

An artificial rainfall experiment based on the seeding of liquid carbon dioxide by aircraft on December 27, 2013, at Saijo, Ehime, in the Inland Sea of Japan

An artificial rainfall experiment based on the seeding of liquid carbon dioxide by aircraft on December 27, 2013, at Saijo, Ehime, in the Inland Sea of Japan

Marine artificial structures as amplifiers of Aurelia aurita s.l. blooms: a case study of a newly installed floating pier

Increase of marine artificial structures, providing more substrate for jellyfish polyps, has been argued to increase jellyfish outbreaks, although no explicit evidence exists. We report a case study demonstrating a remarkable increase of Aurelia aurita s.l. ephyrae after the installation of a floating pier (48 × 6 m) in a fishing port on the Inland Sea of Japan. Monitoring of ephyrae from January 2010, prior to the installation of the floating pier in April 2010, to July 2011, revealed that their time-weighted average density increased 3.5 fold, from 1.1 to 3.9 ephyrae m−3, and the integrated number of ephyrae exported from the port increased 4.3 fold, from 5.7 × 106 to 25 × 106 ephyrae, after the installation. However, in a nearby port, a control site, the abundance of ephyrae decreased by ca. one third during the same period. Monitoring of polyps showed that they initially colonized the undersurface of the pier by August 2010, followed by a rapid population increase. They strobilated from December 2010 to May 2011. We computed the number of ephyrae released from the strobilae to be ca. 25 × 106, very close to the net increase of ephyrae produced and exported from the port. This study corroborates that the installation of an artificial structure provides new a substrate for polyps, which allows them to produce more ephyrae to induce medusa blooms.

Three Unicapsula species (Myxosporea: Trilosporidae) of Asian marine fishes, including the description of Unicapsula setoensis n. sp. in the yellowfin goby (Acanthogobius flavimanus) from the Inland Sea of Japan.

The myxosporean genus Unicapsula (Multivalvulida: Trilosporidae) is defined as having a spore with three unequal shell valves and polar capsules, of which one is prominent and the two other polar capsules are rudimentary. Genetic characterization of members of the genus, currently 11 nominal species, is, at present, unsatisfactory yet when comparing to the closely related genus Kudoa (Multivalvulida: Kudoidae). In the present study, we characterized long ribosomal RNA gene (rDNA) sequences of three Unicapsula spp., namely Unicapsula pyramidata, Unicapsula seriolae, and a novel myxosporean species, Unicapsula setoensis n. sp., from Asian fishes. Elongated plasmodia of U. pyramidata were found in the trunk muscle of Japanese threadfin breams, Nemipterus japonicus, fished off northern Vietnam in the South China Sea. Semitriangular spores, 5.5-6.4 μm in length and 5.6-9.6 μm in width, consisted of three shell valves with two caudal appendages, 7.2-7.4 μm in length. One prominent polar capsule, 2.0-2.4 μm in diameter, was located in the apical shell valve and two rudimentary polar capsules, 0.4-0.5 μm in diameter, in each caudal shell valve. Elongated plasmodia of U. seriolae were found in the trunk muscle of a greater yellowtail, Seriola dumerili, aquacultured in Japan. Semispherical spores, 5.9-7.4 μm in length and 6.3-7.4 μm in width, also consisted of three shell valves and one prominent polar capsule, 3.4-3.8 μm in diameter, with two rudimentary polar capsules, 0.7-1.0 μm in diameter. Plasmodia of U. setoensis n. sp. were found in the trunk muscle of yellowfin gobies, Acanthogobius flavimanus, fished off Hofu, Yamaguchi Prefecture, in the Inland Sea of Japan. Semispherical spores, 5.6-6.9 μm in diameter, displayed three shell valves and one prominent and two rudimentary polar capsules. The former functional polar capsule was 1.9-2.5 μm in diameter and extruded a 9.4-13.8-μm-long polar filament. Nearly the whole length of the 18S rDNA and more than 2,200 bp of the 28S rDNA of the three Unicapsula spp. were sequenced along with nucleotide sequences of the 5.8S rDNA and internal transcribed spacer-1 and spacer-2 of U. pyramidata and U. setoensis n. sp. Molecular genetic analyses supported the morphological species differentiation of U. pyramidata and U. seriolae, and the distinctness of U. setoensis n. sp. from hitherto known species.

Jomon Water Transportation of Obsidian and Volcanic Activity: Excavation and Analyses of the Yokoo Coastal Wetland Site, Japan

This paper reports on the investigation of Yokoo Site, a Jomon site, by the Oita Municipal Board of Education. Yokoo is located in Oita city on Kyushu Island in the western part of the Japanese archipelago. Japanese archaeologists have recognized Yokoo as a Jomon site with a shell mound since it was discovered at the beginning of the twentieth century. Yokoo is one of Japan’s most important sites for the history of archaeology. Until our investigation, the biggest part of the Yokoo site, which is the area without the shell mound, had been obscured and impossible to excavate.The purpose of the research described here was to investigate the structure and characteristics of Yokoo Site using various geo- and environmental archaeological methods. As a result, it was found that Yokoo Settlement was a relay station for the transportation of Himeshiman obsidian along a sea route during the Initial to Late Jomon period. Himeshima, an obsidian resource, was a mountain during the Jomon period, but due to marine transgression is now an island off the coast of the Kunisaki Peninsula. Himeshiman obsidian was transported across the Seto Islands Sea and the Inland Sea of Japan, which formed during the same period. Himeshiman obsidian is an important archaeological material and was transported across the Seto Islands Sea via a marine route in 7900–7300 cal BP. However, geoarchaeological research shows that on one occasion that transportation was interrupted by a natural disaster, the eruption of Kikai Caldera in 7300 cal BP. The Yokoo site shows not only human adaptation to the ongoing marine transgression but also remarkable evidence of an instantaneous human event during this, the greatest volcanic disaster since the formation of the Japanese Archipelago.

瀬戸内海呉港における有鐘繊毛虫類の出現密度, 現存量, 増殖速度, および生産速度の季節的変動

瀬戸内海呉港における有鐘繊毛虫類の出現密度, 現存量, 増殖速度, および生産速度の季節的変動

A new record of the Kumamoto oyster Crassostrea sikamea in the Seto Inland Sea, Japan

We collected 138 Kumamoto like oyster specimens in and around the Nakatsu tidal flat to monitor species diversity. The mitochondrial large subunit of ribosomal DNA (LSrDNA) and the nuclear ribosomal internally transcribed spacer-1 (ITS-1) region were amplified by polymerase chain reaction and restriction fragment length polymorphism analysis, leading to the discovery of the Kumamoto oyster Crassostrea sikamea in the Nakatsu tidal flat. A more accurate species identification using the nucleotide sequences for cytochrome c oxidase subunit I and ITS-1 confirmed the presence of the oysters. These results provide the first evidence of C. sikamea in the Seto Inland Sea of Japan.

Geochemical investigation of selected elements in coastal and riverine sediments from Ube, Kasado, and Suo-Oshima Bays in the western Seto Inland Sea, Southwest Japan

This paper presents the geochemical study of sediments along Ube, Suo-Oshima, and Kasado Bays in the Seto Inland Sea of Japan. We examined the distribution and abundances of 13 elements (As, Pb, Zn, Cu, Ni, Cr, Sr, Ca, Fe, Ti, P, Mn, and total S) in 40 coastal and river sediment samples, to evaluate the factors controlling their abundances, possible sources, and environmental implications. Average concentrations of As, Pb, Zn, Cu, Ni, and Cr at Ube were 12, 26, 86, 16, 43, and 92 mg/kg, 6, 25, 31, 8, 9, and 29 mg/kg at Kasado, and 5, 20, 28, 3, 5, and 18 mg/kg at Suo-Oshima, respectively. Average As, Pb, Zn, and Cr concentrations at Ube were comparable or enriched relative to those of the upper continental crust and Japan upper crust, whereas most major elements, Cu, and Ni were depleted at Kasado and Suo-Oshima. Enrichment factor values show low to moderate enrichment of Zn, Ni, and Cr, whereas As and Pb show significant contamination at some sites, suggesting contributions from anthropogenic sources. Anthropogenic contributions of most metals mainly originate from natural processes; however, As and Pb ranges of 73–79 and 66–81 %, respectively, confirm their anthropogenic contribution. Factor analysis and correlation matrices suggest that elevated metal concentrations at Ube, especially in samples located in the river basin, may be controlled by Fe–Mn oxy-hydroxides. Deposition of metals at Kasado and Suo-Oshima might be controlled by non-ferrous metal (i.e., aluminosilicates), sediment grain size, or source rock composition (granite and gneiss).

A New Conger-like Eel, Muraenesox yamaguchiensis, from the Inland Sea of Japan

A New Conger-like Eel, Muraenesox yamaguchiensis, from the Inland Sea of Japan

Human forcing of the copepod–fish–jellyfish triangular trophic relationship

Copepods, the most abundant planktonic metazoans, constitute an intermediate trophic position between phytoplankton and higher trophic-level animals such as fish and jellyfish. Fish and jellyfish are adversaries because they often compete for prey copepods and also can be prey of each other. The classical food chain represented by phytoplankton–copepod–fish is the main process leading to efficient and sustainable production of fish as human food. At present, more than 75% of world fish stocks are fully or over exploited. On the other hand, jellyfish populations have increased world-wide, particularly in waters under significant human influences. Two such cases are seen in East Asian waters, where massive blooms of moon jellyfish (Aurelia aurita s.l.) and giant jellyfish (Nemopilema nomurai) have repeatedly occurred in recent decades, causing severe damage to local fisheries. In this article, I will review the pivotal role of copepods in marine ecosystems, particularly in the Inland Sea of Japan, where the annual fish catch per unit area is among the world’s highest. Then, I will describe an ongoing ecosystem shift from dominance by fish to dominance by jellyfish as a consequence of human forcing. Finally, I will propose to create “sato-umi”, a coastal sea with high productivity and biodiversity with wise human interaction, where copepod production would most efficiently transforms into food for humans.

Applicability of a Long-Term Wave Hindcast System in the Inner Bay Areas and Seto Inland Sea of Japan Using SDP Measurement-Based Winds

A 45-year wave hindcast system on a nested grid with high space resolution is applied to investigate the long-term wave conditions in the inner bay areas and inland sea of Japan from Tokyo Bay to the western Seto Inland Sea. The system is driven station by station by hourly sea wind distributions evaluated using both the typhoon-embedded analysis wind data archive in the open ocean and the land-based measurement(SDP) wind data in the bay areas. Reasonable agreement between the hindcasts and measurements for wave statistics in each bay area shows that the system is sufficient to closely reproduce the long-term wave conditions in the concerned sea areas but that use of other types of wind data archives with temporal homogeneity may be desirable to more properly evaluate the long-term variation of wave conditions.

Making Scents of Smell: Manufacturing and Consuming Incense in Japan

The academic discourse on smell is characterised by a set of myths, or mode of signification, that cover a broad range of cultural, historical, linguistic, moral, physiological, racial, religious, sexual, social, and symbolic olfactory phenomena, and that include, in particular, smell as an undervalued sense, the articulation of smell, and its association with ritual practices. These myths frame the discussion of the processes by which incense is produced in Japan, as well as of the various challenges facing a manufacturer with regard to consistency of raw materials, kneading blended materials, and drying formed incense sticks. The article then concentrates on a group of incense manufacturers located on the western coast of Awaji Island in the Inland Sea of Japan, and suggests that it is access to, and successful management of, olfactory knowledge that enables a subcontracted supplier to become independent by producing his own incense brands. It concludes by tracing connections between smell, transiti...

Construction of a Data Set of 45-Year Sea Wind Distribution on the Inner Bay and Inland Sea of Japan Using SDP Winds Measurement Data

Construction of a Data Set of 45-Year Sea Wind Distribution on the Inner Bay and Inland Sea of Japan Using SDP Winds Measurement Data

A 45-Year Wave Hindcast System in the Inner Bay Areas and Inland Sea of Japan Using SDP Measurements-Based Winds -Tokyo Bay Case-

A long-term wave hindcast system applicable for the wave computations over a 45-year period at an arbitrary location of Tokyo Bay area is reconstructed. Hourly sea wind distributions estimated by making use of an analogy between land-based SDP wind measurement data and coast- and sea-based wind measurement data are given on the coastal sea area and those made by recompiling the NCEP/NCAR reanalysis surface wind product on the open ocean. Wave computation is based on a backward ray tracing model on a nested grid with very high space resolution. Comparison between hindcasts and measurements for wave height over a long period of 10 to 23 years at 5 stations situated inside and outside of Tokyo Bay verified a reasonable performance of the system.

A redescription of Pseudorhabdosynochus epinepheli (Yamaguti, 1938), the type-species of Pseudorhabdosynochus Yamaguti, 1958 (Monogenea: Diplectanidae), and the description of P. satyui n. sp. from Epinephelus akaara off Japan.

Pseudorhabdosynochus epinepheli (Yamaguti, 1938) has been recorded from a variety of hosts, mainly groupers. All type-specimens of Diplectanum epinepheli Yamaguti, 1938, Pseudorhabdosynochus epinepheli Yamaguti, 1958 and Cycloplectanum hongkongensis Beverley-Burton & Suriano, 1981 are figured: it is concluded, as did Kritsky & Beverley-Burton (1986), that the three species are synonymous. In addition, numerous monogenean specimens from a deep-sea grouper, Epinephelus chlorostigma, collected off New Caledonia, South Pacific, were prepared using various methods and described. These specimens are also conspecific with P. epinepheli (Yamaguti, 1938) and represent a new geographical record. This species has a sclerotised vagina with a very characteristic primary chamber. The simultaneous presence of P. lantauensis (Beverley-Burton & Suriano, 1981) and P. epinepheli was noted in both type-slides of D. epinepheli from Japan (host: E. akaara) and C. hongkongensis from Hong Kong (host: E. bruneus). Several causes are suspected for the alleged 'generalist' character of P. epinepheli, including the misidentification of either fish or monogeneans and the accidental exchanges of monogeneans between fishes of different species kept alive in the same tank. Finally, the confirmed list of hosts of P. epinepheli includes E. akaara, E. awoara and E. chlorostigma; it is suggested that the latter, a widespread deep-sea fish, serves as a reservoir for the infection of the other species, which are associated with shallow waters. P. satyui n. sp. is described from two specimens found on slides from E. akaara (from the Inland Sea of Japan) deposited by Yamaguti; the new species has a sclerotised vagina with characteristic spherical chambers.

Carotenoids in a Corynebacterineae,Gordonia terraeAIST-1: Carotenoid Glucosyl Mycoloyl Esters

We isolated a strain of Corynebacterineae from surface seawater from the Inland Sea of Japan. This strain, AIST-1, was determined to be a strain of Gordonia terrae based on its 16S rRNA gene sequence. The colony was red-colored, and the pigments were identified to be carotenoid derivatives. The structures of two major carotenoids were (2'S)-deoxymyxol 1'-glucoside, a dihydroxyl derivative of gamma-carotene with 12 conjugated double bonds, and (2'S)-4-ketodeoxymyxol 1'-glucoside. Their glucosyl acyl esters and mycoloyl esters were also identified. While these carotenoid moieties have been found in only a few other bacteria, the carotenoid mycoloyl esters are novel carotenoid derivatives. The type strain of G. terrae NBRC 10016T also contained the same carotenoids, but the composition of the two carotenoid glucosides was low and the total carotenoid content was less than one tenth of that of strain AIST-1.